Hematopoietic stem cells (HSCs) have the capacity to both self-renew and differentiate into all mature blood cell types, making them promising treatments for a variety of diseases. However, the mechanisms involved in engraftment—when the cells start to grow and make healthy blood cells after being transplanted into a patient—are poorly understood. A recent study led by researchers at Massachusetts General Hospital (MGH) and Boston University School of Medicine has revealed the unique signature of genes expressed by HSCs capable of undergoing this process. The findings, which are published in Nature Communications, could enable scientists to expand these cells outside of the body or to convert other types of stem cells into cells that can repopulate the blood system.